feat: real data pipeline — market data, DB persistence, portfolio sync, signal-trade linkage

Wire the trading bot to real Alpaca market data and persist pipeline
state to the database so the dashboard displays live information.

- Add market-data service fetching OHLCV bars from Alpaca, publishing
  to market:bars Redis Stream; signal generator consumes bars and
  injects current_price into signals for position sizing
- Sentiment analyzer now persists Article + ArticleSentiment rows to
  DB after scoring, with duplicate and error handling
- API gateway runs a background portfolio sync task that snapshots
  Alpaca account state into PortfolioSnapshot/Position DB tables
  during market hours
- TradeSignal carries a signal_id UUID; signal generator and trade
  executor both persist their records to DB with cross-references
- 303 unit tests pass (57 new tests added)

.env.example

@@ -10,6 +10,16 @@ TRADING_LOG_LEVEL=INFO
 TRADING_ALPACA_API_KEY=your_api_key_here
 TRADING_ALPACA_SECRET_KEY=your_secret_key_here
 TRADING_ALPACA_BASE_URL=https://paper-api.alpaca.markets
+TRADING_PAPER_TRADING=true
+
+# Market data service — watchlist tickers (comma-separated)
+TRADING_WATCHLIST=["AAPL","TSLA","NVDA","MSFT","GOOGL"]
+TRADING_BAR_TIMEFRAME=5Min
+TRADING_POLL_INTERVAL_SECONDS=60
+TRADING_HISTORICAL_BARS=100
+
+# Portfolio sync interval (seconds, api-gateway background task)
+TRADING_SNAPSHOT_INTERVAL_SECONDS=60
 
 # JWT — REQUIRED, generate with: python -c "import secrets; print(secrets.token_hex(32))"
 TRADING_JWT_SECRET_KEY=